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NASA NTRS1993

High speed transition prediction

The main objective of this work period was to develop, maintain and exercise state-of-the-art methods for transition prediction in supersonic flow fields. Basic state and stability codes, acquired during the last work period, were exercised and applied to calculate the properties of various flowfields. The development of a code for the prediction of transition location using a currently novel method (the PSE or Parabolized Stability Equation method), initiated during the last work period and continued during the present work period, was cancelled at mid-year for budgetary reasons. Other activities during this period included the presentation of a paper at the APS meeting in Tallahassee, Florida entitled 'Stability of Two-Dimensional Compressible Boundary Layers', as well as the initiation of a paper co-authored with H. Reed of the Arizona State University entitled 'Stability of Boundary Layers'.

Gasperas, Gediminis↗

DOE OSTI2025

Multistate Geometry of Shift Current and Polarization

The quantum metric and Berry curvature capture essential properties of nontrivial Bloch states and underpin many fascinating phenomena. However, it becomes increasingly evident that a more comprehensive understanding of quantum state geometry is necessary to explain properties involving Bloch states of multiple bands, such as optical transitions. To this end, we employ quantum state projectors to develop an explicitly gauge-invariant formalism and demonstrate its power with applications to nonlinear optics and the theory of electronic polarization. We provide a simple expression for the shift current that resolves its precise relation to the moments of electronic polarization, clarifies the treatment of band degeneracies, and reveals its decomposition into the sum of the skewness of the occupied states and intrinsically multistate geometry. The projector approach is applied to calculate nonlinear optical properties of transition metal dichalcogenides (TMDs) layers, using previously calculated minimal tight-binding models, and demonstrated analytically on a three-band generalization of the Rice-Mele chain to elucidate the different contributions. We close with comments on further applications of the projector operator approach to multistate geometry.

electric polarization↗

NASA NTRS1994

Calculation of (12)C(16)O and (13)C(16)O X(1)Sigma(+) rovibrational intensities for v less than or equal to 20 and J less than or equal to 150

Improved electric dipole transition matrix elements for rovibrational transitions in the ground state X(1)Sigma(+) of (12)C(6)O and (13)C(16)O are calculated for all the delta v = +1, +2, and +3 transitions for which v less than or equal to 20 and J less than or equal to 150. We have fitted polynomials to these matrix elements as a function of the parameter m which is defined in terms of the lower state angular momentum quantum number J. These convenient to use polynomial representations are given in Tables 1-4 for (12)C(16)O and in Tables 5-8 for (13)C(16)O. We observe that there is intensity enhancement due to vibration-rotation interaction for the P-branch transitions at the expense of the R-branch transitions for delta v = +1. This enhancement can be as large as 40% at the highest J. For the delta v = +2 and +3 transitions, the R-branch transitions are enhanced by as much as a factor of 2.75 and 10 at the highest J, respectively. The P-branch transitions exhibit only minor decreases. Comparisons with previous calculations show good agreement for the delta v = +1 transitions. The comparison for delta v = +2 and +3 transitions show differences as large as a factor of 5.

Goorvitch, D.↗

DOE OSTI2021

Intertwined Topological and Magnetic Orders in Atomically Thin Chern Insulator MnBi 2 Te 4

The interplay between band topology and magnetic order plays a key role in quantum states of matter. MnBi 2 Te 4 , a van der Waals magnet, has recently emerged as an exciting platform for exploring Chern insulator physics. Its layered antiferromagnetic order was predicted to enable even-odd layer-number dependent topological states, supported by promising edge transport measurements. Furthermore, it becomes a Chern insulator when all spins are aligned by an applied magnetic field. However, the evolution of the bulk electronic structure as the magnetic state is continuously tuned and its dependence on layer number remains unexplored. Here, employing multimodal probes, we establish oneto-one correspondence between bulk electronic structure, magnetic state, topological order, and layer thickness in atomically thin MnBi 2 Te 4 devices. As the magnetic state is tuned through the canted magnetic phase, we observe a band crossing, i.e., the closing and reopening of the bulk bandgap, corresponding to the concurrent topological phase transition. Surprisingly, we find that the even- and odd-layer number devices exhibit a similar topological phase transition coupled to magnetic states, distinct from recent theoretical and experimental reports. Our findings shed new light on the interplay between band topology and magnetic order in this newly discovered topological magnet and validate the band crossing with concurrent measurements of topological invariant in a continuously tuned topological phase transition.

36 MATERIALS SCIENCE↗

DOE OSTI2021

The Role of State Utility Regulators in a Just and Reasonable Energy Transition: Examining Regulatory Approaches to the Economic Impacts of Coal Retirements

The ongoing trend of coal retirements has disproportionately affected the socioeconomic health of communities where power plants are located. For many public utility commissions, these impacts have led to important questions around the scope of PUCs’ statutory authority to analyze, consider and mitigate losses to host communities within their role as utility regulators. Due largely to variations in state legislative charges, commissions have taken different approaches to articulating what lies within the public interest.This report examines the authority of PUCs across the country to consider non-energy economic impacts beyond direct ratepayer effects, and summarizes approaches that PUCs, utilities and other stakeholders have used to mitigate the economic fallout of coal retirements, specifically.

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2021

Structure and dynamical properties of two-dimensional dusty plasmas on one-dimensional periodic substrates

In the presence of the substrate, various structural and dynamical properties of two-dimensional dusty plasma (2DDP) were investigated using Langevin dynamical simulations. This paper reviews a series of results of the structural and dynamical properties of 2DDP modified by one-dimensional periodic substrates (1DPSs) as follows. First, when the depth of the 1DPS increases gradually, it is found that the static structural order of 2DDP along each potential well of the 1DPS increases first, and then decreases gradually. When the width of the 1DPS increases gradually, the particle arrangement in each potential well of the 1DPS changes from one straight row gradually to two rows, including the stable zigzag structure. Second, when there are two rows in each potential well of the 1DPS, the phonon spectra are split into two branches, corresponding to the breathing and sloshing modes, respectively. In addition, due to the pure repulsion between dust particles, from the obtained phonon spectra, the sloshing wave propagates backward at small wave numbers. Third, the calculated mean-square displacement (MSD) shown that, at the intermediate timescale between the initial ballistic and final diffusive motions, the particle motion tends to be more subdiffusive while the depth of the 1DPS increases. While the width of the 1DPS increases gradually, the long-time diffusive motion first increases, then decreases, and finally increases again, exhibiting the oscillation-like diffusion, due to the stable zigzag structure. Finally, when an external direct-current driving force is applied on all particles of 2DDP, three different depinning phases are discovered, which are the pinned, disordered plastic flow, and moving ordered states, respectively, as the driving force increases from zero. In addition, the continuous/discontinuous property of the phase transition between these different depinning states is investigated, showing that the transition property is modulated by the depth of the applied 1DPS

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2026

Lifetimes of low-lying levels in 158 Gd

The low-lying structure of the well-deformed nucleus 158 Gd has been revisited to elucidate the nature of the low-lying states in 158 Gd. Earlier (p, t) studies identified numerous 0 + states below 4.3 MeV, prompting questions about whether these states correspond to collective vibrations or shape coexistence. New and previously reported (n, n' γ) measurements are combined, including γ-γ coincidences, excitation functions, and angular distributions, to extract lifetimes and transition probabilities for 44 excited states up to 2.7 MeV, including 32 previously unmeasured levels. Our results confirm or revise γ-ray placements and provide detailed transition strengths, revealing both weakly collective and strongly enhanced B(E2) and B(E1) transition probabilities. In particular, a tentative 0 + state at 2437.8 keV exhibits a strong interband B(E2) transition, which may be a candidate for a possible two-phonon (ββ) excitation. Systematic comparisons with neighboring Gd isotopes, Hartree–Fock–Bogoliubov, and interacting-boson model predictions suggest that the first excited 0 + state in 158 Gd is predicted to be a β-vibration, although it is weakly collective.

158Gd↗

NASA NTRS1988

Markov chains for testing redundant software

A preliminary design for a validation experiment has been developed that addresses several problems unique to assuring the extremely high quality of multiple-version programs in process-control software. The procedure uses Markov chains to model the error states of the multiple version programs. The programs are observed during simulated process-control testing, and estimates are obtained for the transition probabilities between the states of the Markov chain. The experimental Markov chain model is then expanded into a reliability model that takes into account the inertia of the system being controlled. The reliability of the multiple version software is computed from this reliability model at a given confidence level using confidence intervals obtained for the transition probabilities during the experiment. An example demonstrating the method is provided.

White, Allan L.↗

DOE OSTI2025

Observation of Topological Chirality Switching Induced Freezing of a Skyrmion Crystal

Magnetic skyrmions are topologically protected quasi-particles with a well-defined chirality. Control over their chirality is proposed as an additional feature for encoding data bits or as qubits in quantum computing due to their high efficiency and stability against achiral magnetic textures. Here it is shown that an in-plane magnetic field can be utilized to reshape the energy barriers between different skyrmionic bubbles (e.g., Bloch type, type-II) enabling spontaneous chirality fluctuations with a frequency that increases with the strength of the in-plane field. The insulating van der Waals ferromagnet CrBr3 is used as an archetypal system for low damping, reduced energy dissipation and a high number of magnetic phases to capture the chirality dynamics in real time through cryo-Lorentz transmission electron microscopy. It is observed that the interplay between the intrinsic Dzyaloshinskii–Moriya interaction and out-of-plane field biased the chirality dynamics, favoring one handedness over the other. A remarkable consequence of the spontaneous chirality switching mechanism is that it induces a freezing (or crystallization) process in the skyrmion lattice. As the bubbles fluctuate between Bloch and type-II they elongate and shrink parallel to the in-plane field. Subsequently, the overall lattice crystallizes along the in-plane field direction, inducing a phase transition from a disordered liquid state to a hexatic phase where skyrmions are highly ordered resembling that of a solid. The results indicate chirality as an active element in the creation of topologically protected skyrmion crystals unveiling pathways toward chiral spintronic device platforms with tunable embedded configuration.

2D Phase Transition↗

DOE OSTI2021

A three-step model of high harmonic generation using complex classical trajectories

Highlights: • Rigorous trajectory formulation of strong field physics and high harmonic generation. • The Coulomb ground state is represented by an ensemble of complex trajectories. • Trajectories transition seamlessly from the ground state to ionization or recollision. • The ionized wavepacket is reproduced well from the complex trajectories. • Classically allowed and forbidden processes are treated in a single framework. We present a new trajectory formulation of high harmonic generation that treats classically allowed and classically forbidden processes within a single dynamical framework. Complex trajectories orbit the nucleus, producing the stationary Coulomb ground state. When the field is turned on, these complex trajectories continue their motion in the field-dressed Coulomb potential and therefore tunnel ionization, unbound evolution and recollision are described within a single, seamless framework. The new formulation can bring mechanistic understanding to a broad range of strong field physics effects.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS1972

Quartz and feldspar glasses produced by natural and experimental shock.

Refractive index, density, and infrared absorption studies of naturally and experimentally shocked-produced glasses formed from quartz, plagioclase, and alkali-feldspar confirm the existence of two main groups of amorphous forms of the framework silicates: solid-state and liquid-state glasses. These were apparently formed as metastable release products of high-pressure-phases above and below the glass transition temperatures. Solid-state glasses exhibit a series of structural states with increasing disorder caused by increasing shock pressures and temperatures. They gradually merge into the structural state of fused minerals similar to that of synthetic glasses quenched from a melt. Shock-fused alkali feldspars can, however, be distinguished from their laboratory-fused counterparts by infrared absorption and by higher density.

Stoeffler, D.↗

NASA NTRS1992

On the decomposition of synchronous state mechines using sequence invariant state machines

This paper presents a few techniques for the decomposition of Synchronous State Machines of medium to large sizes into smaller component machines. The methods are based on the nature of the transitions and sequences of states in the machine and on the number and variety of inputs to the machine. The results of the decomposition, and of using the Sequence Invariant State Machine (SISM) Design Technique for generating the component machines, include great ease and quickness in the design and implementation processes. Furthermore, there is increased flexibility in making modifications to the original design leading to negligible re-design time.

Hebbalalu, K.↗

NASA NTRS2005

SCB Quantum Computers Using iSWAP and 1-Qubit Rotations

Units of superconducting circuitry that exploit the concept of the single- Cooper-pair box (SCB) have been built and are undergoing testing as prototypes of logic gates that could, in principle, constitute building blocks of clocked quantum computers. These units utilize quantized charge states as the quantum information-bearing degrees of freedom. An SCB is an artificial two-level quantum system that comprises a nanoscale superconducting electrode connected to a reservoir of Cooper-pair charges via a Josephson junction. The logical quantum states of the device, .0. and .1., are implemented physically as a pair of charge-number states that differ by 2e (where e is the charge of an electron). Typically, some 109 Cooper pairs are involved. Transitions between the logical states are accomplished by tunneling of Cooper pairs through the Josephson junction. Although the two-level system contains a macroscopic number of charges, in the superconducting regime, they behave collectively, as a Bose-Einstein condensate, making possible a coherent superposition of the two logical states. This possibility makes the SCB a candidate for the physical implementation of a qubit. A set of quantum logic operations and the gates that implement them is characterized as universal if, in principle, one can form combinations of the operations in the set to implement any desired quantum computation. To be able to design a practical quantum computer, one must first specify how to decompose any valid quantum computation into a sequence of elementary 1- and 2-qubit quantum gates that are universal and that can be realized in hardware that is feasible to fabricate. Traditionally, the set of universal gates has been taken to be the set of all 1-qubit quantum gates in conjunction with the controlled-NOT (CNOT) gate, which is a 2-qubit gate. Also, it has been known for some time that the SWAP gate, which implements square root of the simple 2-qubit exchange interaction, is as computationally universal as is the CNOT operation.

Williams, Colin↗

DOE OSTI2021

Collective states and charge density waves in the group IV transition metal trichalcogenides

It has been nearly a century since the original mechanism for charge density wave (CDW) formation was suggested by Peierls. Since then, the term has come to describe several related concepts in condensed matter physics, having their origin in either the electron–phonon or electron–electron interaction. The vast majority of CDW literature deals with systems that are metallic, where discussions of mechanisms related to the Fermi surface are valid. Recently, it has been suggested that semiconducting systems such as TiS 3 and TiSe 2 exhibit behavior related to CDWs. In such cases, the origin of the behavior is more subtle and intimately tied to electron–electron interactions. We introduce the different classifications of CDW systems that have been proposed and discuss work on the group IV transition metal trichalcogenides (TMTs) (ZrTe 3 , HfTe 3 , TiTe 3 , and TiS 3 ), which are an exciting and emergent material system whose members exhibit quasi-one-dimensional properties. TMTs are van der Waals materials and can be readily studied in the few-layer limit, opening new avenues to manipulating collective states. We emphasize the semiconducting compound TiS 3 and suggest how it can be classified based on available data. Although we can conjecture on the origin of the CDW in TiS 3 , further measurements are required to properly characterize it.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Uranium Chemistry: Identifying the Next Frontiers

While uranium is the most extensively studied actinide in terms of chemical properties, there remains much to be explored about its fundamental chemistry. Organometallic and organoactinide chemistry first emerged in the 1950s with research that found inspiration from transition-metal chemistry with the synthesis and characterization of uranocene, expanding new opportunities for organoactinide chemistry. Since then, a significant amount of research has pursued many avenues characterizing the fundamental nature of the f orbitals and their modes of bonding as well as their potential in catalysis. Uranium(III/IV) arene complexes dominate much of uranium organometallic chemistry, with bonding interactions stabilized by δ-back-bonding. Recent additions to this area of chemistry include the first UI and new additions of U II organouranium compounds. Uranium–transition metal complexes are still rare and maintain U IV oxidation states, with variable bond lengths determining the transition-metal oxidation state. Resultant reactivities are discussed as synthetic complexes, and unique bonding and coordination motifs are highlighted. In conclusion, this Viewpoint will focus on significant developments in uranium chemistry from the last 15 years while considering key areas for future research.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

NASA NTRS1984

Far-infrared laser magnetic resonance of vibrationally excited CD2

The detection of 13 rotational transitions in the first excited bending state (010) of CD2 using the technique of far-infrared laser magnetic resonance spectroscopy is reported. Molecular parameters for this state are determined from these new data together with existing infrared observations of the v(2) band. Additional information on the ground vibrational state (000) is also provided by the observation of a new rotational transition, and this is combined with existing data to provide a refined set of molecular parameters for the CD2 ground state. One spectrum has been observed that is assigned as a rotational transition within the first excited symmetric stretching state (100) of CD2. These data will be of use in refining the structure and the potential function of the methylene radical.

Evenson, K. M.↗

DOE OSTI2023

Optimizing Renewable Ammonia Production for a Sustainable Fertilizer Supply Chain Transition

Local renewable ammonia production using electrolytic hydrogen is an emerging approach to alleviate emissions attributed to synthetic nitrogen fertilizer production while also insulating against fluctuations in fertilizer prices and mitigating transportation costs and emissions. However, replacing ammonia currently produced using fossil fuels will not be immediate. To this end, we develop a supply chain transition model, which first optimizes the design and hourly operation of new renewable ammonia facilities to minimize production costs and then optimizes the annual installation timing, production scale, and location of these new renewable facilities along with ammonia transportation to meet county resolution demands. The objective is to augment and eventually replace conventional ammonia market imports in an economically competitive manner. We performed a case study for Minnesota's ammonia supply chain and found that a full transition to in-state renewable production by 2032 is optimal. This is incentivized by the U.S. federal government's clean hydrogen production credits. This transition results in 99 % reduction in carbon intensity along with stable supply costs below $475 per metric tonne. New renewable production facilities are an order of magnitude smaller than existing conventional plants. They use both wind and solar resources and operate dynamically to minimize expensive battery and hydrogen storage capacities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

The dual of a tidal force in the D1D5 CFT

It was demonstrated that a string probe falling radially within a superstratum geometry would experience tidal forces. These tidal forces were shown to excite the string by converting its kinetic energy into stringy excitations. Using the AdS/CFT correspondence we seek to understand this behavior from the perspective of the dual D1D5 CFT. To study this process we turn on an interaction of the theory which is described by a deformation operator. We start with an initial state which is dual to a graviton probe moving within the superstratum geometry. We then use two deformation operators to compute transition amplitudes between this state and a final state that corresponds to stringy excitations. We show that this amplitude grows as t 2 with t being the amount of time for which the deformation operators are turned on. We argue that this process in the CFT is suggestive of the tidal effects experienced by the probe propagating within the dual superstratum geometry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗